The present invention relates to a vehicle turn signal device that activates a turn signal in accordance with the operation of an operation lever, which is arranged in a vehicle, and deactivates the turn signal in accordance with a rotating operation of a steering wheel.
As well known in the art, a vehicle includes a turn signal device for switching a turn signal between an activated state and a deactivated state in accordance with the operation of an operation lever and a steering wheel by a driver. FIG. 1 is a plan view showing an operation lever and steering wheel of a vehicle. A turn signal device generally activates the turn signal (not shown) on the right side or left side of the vehicle when the driver operates an operation lever 11, which is arranged on a steering column 10 of the vehicle. The turn signal device also deactivates the turn signal in accordance with the rotating operation of the steering wheel 12 performed by the driver. Japanese Laid-Open Patent Publication No. 11-70833 describes an example of such a turn signal device.
The turn signal device described in Japanese Laid-Open Patent Publication No. 11-70833 includes a rotation angle sensor for detecting a rotation angle θ from a neutral position of the steering wheel 12. The turn signal is deactivated based on the rotation angle θ detected by the rotation angle sensor. For example, after activating the right turn signal of the vehicle, the driver rotates the steering wheel 12 to the right (operation in the direction indicated by arrow a1 in FIG. 1). The driver then rotates the steering wheel 12 to the left (operation in the direction indicated by arrow a2 in FIG. 1) to return the steering wheel 12 to a neutral position. The turn signal device calculates a returning rotation angle θb when the rotating direction of the steering wheel 12 is reversed based on the rotation angle θ detected by the rotation angle sensor. The turn signal device deactivates the turn signal when the calculated returning rotation angle θb reaches a cancellation return angle θs.
In the prior art turn signal device, the value of the cancellation return angle θs is set to automatically deactivate the turn signal even when a temporal change in the rotation angle θ is extremely small, such as when the driver activates the turn signal to change lanes while driving on a highway. This eliminates the need to manually deactivate the turn signal and significantly improves convenience.
However, in the turn signal device, for example, the size of the vehicle or the width of a road varies the rotation angle θ at which the steering wheel 12 is returned. This slightly varies the timing at which the turn signal is deactivated.
FIGS. 2 and 3 show the rotation angle θ of the steering wheel 12 when it is returned. FIG. 2 shows the movement of the vehicle and temporal changes in the rotation angle θ when the driver changes lanes to a right lane LR from a left lane LL when driving along a narrow road. FIG. 3 shows the movement of the vehicle and temporal changes in the rotation angle θ when the driver changes lanes to a right lane LR from a left lane LL when driving along a wide road. In FIGS. 2B and 3B, the value of the rotation angle θ when the steering wheel 12 is positioned at the neutral position is indicated as “0°”. The rotation angle θ changes to a negative value when the steering wheel 12 is rotated to the right and to a positive value when the steering wheel 12 is rotated to the left.
As shown in FIGS. 2A and 2B, when changing lanes along a narrow road, the driver operates the operation lever 11 at time t10 to activate the right turn signal of the vehicle. Then, the driver starts to change lanes at time t11, the vehicle crosses a divider line w at time t13, and the lane change is completed at time t15. In this case, the rotation angle θ decreases after time t11, reaches a minimum value θmin at time t12, and increases after time t12. The prior art turn signal device described in Japanese Laid-Open Patent Publication No. 11-70833 starts to calculate the returning rotation angle θb at time t12 when the rotation angle θ reaches the minimum value θmin. Then, the prior art turn signal device deactivates the turn signal at time ta when the returning rotation angle θb reaches the cancellation return angle θs. Thus, when the width of the road is narrow like in FIG. 2A, the turn signal is deactivated after the vehicle crosses the divider line w, that is, when the vehicle enters the right lane LR.
As shown in FIGS. 3A and 3B, when changing lanes along a wide road, the driver operates the operation lever 11 at time t20 to activate the right turn signal of the vehicle. Then, the driver starts to change lanes at time t21, the vehicle crosses the divider line w at time t23, and the lane change is completed at time t25. Compared to when changing lanes along the narrow road, on the wide road, the rotation angle θ varies more greatly and takes a smaller minimum value θmin. In this case as well, the prior art turn signal device described in Japanese Laid-Open Patent Publication No. 11-70833 starts to calculate the returning rotation angle θb at time t22 when the rotation angle θ reaches the minimum value θmin. Then, the prior art turn signal device deactivates the turn signal at time tb when the returning rotation angle θb reaches the cancellation return angle θs. In this case, however, the turn signal is deactivated before the vehicle crosses the divider line w, that is, before the vehicle enters the right lane LR. This may result in the driver of a following vehicle mistakenly believing that the driver of the preceding vehicle does not intend to change lanes.
Accordingly, there is still room for improvement with the prior art turn signal device with regards to the reliability of the deactivation function of the turn signal.